The structures of sodium niobate between 480° and 575°C, and their relevance to soft-phonon modes
- 1 October 1972
- journal article
- research article
- Published by Taylor & Francis in Philosophical Magazine
- Vol. 26 (4), 995-1014
- https://doi.org/10.1080/14786437208226972
Abstract
The structures of NaNb03 in the S phase (480°-520°c) and T1 phase (520°-575°c) have been determined by use of the octahedron tilting schemes of Glazer. Both phases are orthorhombic with unit cell edges approximately twice those of ideal perovskite; their space groups are Pnmm and Ccmm, respectively. An explanation of the T2 to T1 (575°c) transition is given in terms of a soft phonon mode at q = 1/2 1/2 1/2 A comparison is made with the low-temperature transitions in KMnF3.Keywords
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